Drinking water salinity and blood pressure in coastal Bangladesh: follow-up of a population-based cohort in a climate-vulnerable region
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Author(s)
Type
Journal Article
Abstract
Objectives
To investigate the association between drinking-water sodium concentration and blood pressure among
non-pregnant women living in a high-salinity, climate-vulnerable coastal region of Bangladesh.
Design
Follow-up study of women originally enrolled in a population-based study conducted during pregnancy
between 2009 and 2011.
Setting
Rural coastal sub-district in southwest Bangladesh affected by saltwater intrusion and seasonal
drinking-water insecurity.
Participants
Of 1,208 women enrolled in the original study, 900 were located in 2018 and 740 non-pregnant women
were re-enrolled and included in the present analysis. Eligible participants were women from the original
study who were alive and still residing in the study area; women who had migrated, could not be located,
declined participation, or were pregnant at follow-up were excluded.
Primary and secondary outcome measures
The primary outcome was blood pressure, measured using a standardised protocol. Main exposure
was sodium concentration in household drinking water and reported drinking-water source. Secondary analyses assessed temporal changes in drinking-water sodium between 2009 and 2018 and associations with water source, perceived taste and changes in exposure over time.
Results
Mean sodium concentration in household drinking water was highest in groundwater/tubewell users
(933 mg/L, SD 372). Approximately 22% of women consumed drinking water contributing up to 94% of
the WHO-recommended maximum daily sodium intake, assuming 2 L/day consumption. Sodium concentrations increased in seven of nine administrative unions between 2009 and 2018 (p=0.013). Compared with women consuming water containing <200 mg/L sodium, exposure to >1,000 mg/L was associated with higher odds of raised diastolic blood pressure (adjusted OR 2.30, 95% CI 1.40 to 3.77; p=0.001). Restricted cubic spline and piecewise regression models suggested a non-linear association, with a threshold near 1,000 mg/L. No statistically significant association was observed for systolic blood pressure.
Conclusions
High sodium concentrations in drinking water were associated with elevated diastolic blood pressure
among women in coastal Bangladesh. Drinking-water salinity may represent an under-recognised
cardiovascular risk in climate-vulnerable coastal populations. These findings support the need for
salinity surveillance, climate-resilient low-sodium drinking-water supplies, and further research to inform
health-based standards for sodium in drinking water.
Trial registration
Not applicable.
To investigate the association between drinking-water sodium concentration and blood pressure among
non-pregnant women living in a high-salinity, climate-vulnerable coastal region of Bangladesh.
Design
Follow-up study of women originally enrolled in a population-based study conducted during pregnancy
between 2009 and 2011.
Setting
Rural coastal sub-district in southwest Bangladesh affected by saltwater intrusion and seasonal
drinking-water insecurity.
Participants
Of 1,208 women enrolled in the original study, 900 were located in 2018 and 740 non-pregnant women
were re-enrolled and included in the present analysis. Eligible participants were women from the original
study who were alive and still residing in the study area; women who had migrated, could not be located,
declined participation, or were pregnant at follow-up were excluded.
Primary and secondary outcome measures
The primary outcome was blood pressure, measured using a standardised protocol. Main exposure
was sodium concentration in household drinking water and reported drinking-water source. Secondary analyses assessed temporal changes in drinking-water sodium between 2009 and 2018 and associations with water source, perceived taste and changes in exposure over time.
Results
Mean sodium concentration in household drinking water was highest in groundwater/tubewell users
(933 mg/L, SD 372). Approximately 22% of women consumed drinking water contributing up to 94% of
the WHO-recommended maximum daily sodium intake, assuming 2 L/day consumption. Sodium concentrations increased in seven of nine administrative unions between 2009 and 2018 (p=0.013). Compared with women consuming water containing <200 mg/L sodium, exposure to >1,000 mg/L was associated with higher odds of raised diastolic blood pressure (adjusted OR 2.30, 95% CI 1.40 to 3.77; p=0.001). Restricted cubic spline and piecewise regression models suggested a non-linear association, with a threshold near 1,000 mg/L. No statistically significant association was observed for systolic blood pressure.
Conclusions
High sodium concentrations in drinking water were associated with elevated diastolic blood pressure
among women in coastal Bangladesh. Drinking-water salinity may represent an under-recognised
cardiovascular risk in climate-vulnerable coastal populations. These findings support the need for
salinity surveillance, climate-resilient low-sodium drinking-water supplies, and further research to inform
health-based standards for sodium in drinking water.
Trial registration
Not applicable.
Date Issued
2026-07-01
Date Acceptance
2026-06-09
Citation
BMJ Open, 2026, 16 (7)
ISSN
2044-6055
Publisher
BMJ Publishing Group
Journal / Book Title
BMJ Open
Volume
16
Issue
7
Copyright Statement
© Author(s) (or their employer(s)) 2026. Re-use permitted under CC BY. Published by BMJ Group.
License URL
Publication Status
Published
Article Number
e116453
Date Publish Online
2026-07-01